Visual Understanding Environment - Visual Understanding Environment (VUE) is a mind-mapping and concept-mapping tool.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Xmind - Xmind is a brainstorming and mind mapping application.
FreeMind - FreeMind is a premier free mind-mapping software written in Java.
vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.